KR20140037070A - Methods and arrangements for communications in low power wireless networks - Google Patents

Abstract

Embodiments may include an Orthogonal Frequency Division Multiplexing (OFDM) system operating in the 1 GHz and below frequency bands. In many embodiments, physical layer logic may implement repetition logic that repeats a portion of the data stream to increase the capability of the receiving device to detect and decode the data stream. In some embodiments, the iterative logic may include a preamble repeater that repeats the training and / or signal fields. In another embodiment, the iterative logic may include a payload repeater that repeats the payload more than once. Another embodiment includes a receiving device comprising a correlator, wherein the correlator correlates the repeated preamble symbols to detect communication from the transmitting device. The receiving device may include correction logic to correct the data stream from the communication signal based on the repetition of the payload in the data stream.

Description

[0001] METHODS AND ARRANGEMENTS FOR COMMUNICATIONS IN LOW POWER WIRELESS NETWORKS [0002]

The present invention relates to a method and apparatus for communication in a low power wireless network.

Embodiments relate to the field of wireless communications. More specifically, embodiments relate to the field of communication protocols between wireless transmitters and receivers.

1 illustrates one embodiment of an exemplary wireless network that includes a plurality of communication devices including multiple fixed or mobile communication devices.
FIG. 1A illustrates an embodiment of a physical layer protocol data unit generated by the short training field repeater logic of FIG.
FIG. 2 illustrates an embodiment of an apparatus for generating and transmitting Orthogonal Frequency Division Multiplexing (OFDM) based communication in a wireless network.
3 illustrates an embodiment of a flow diagram for transmitting communications to the transmitter illustrated in FIG.
FIG. 4 illustrates an embodiment of a flow diagram for receiving communications to the receiver illustrated in FIG.

The following describes in detail the novel embodiments shown in the accompanying drawings. However, many of the details provided are not intended to limit the foreseeable variations of the described embodiments, on the contrary, the claims and detailed description are within the spirit and scope of the subject matter defined in the appended claims. It covers all amendments, equivalents, and options. The following detailed description is designed to enable those skilled in the art to understand the embodiments.

It is to be understood that the phrase "one embodiment", "an embodiment", "an example embodiment", "various embodiments" and the like indicate that the described embodiment (s) of the present invention may include a particular feature, , It is to be understood that not every embodiment necessarily includes this particular feature, structure, or characteristic. Also, the phrase "in one embodiment " used repeatedly is not necessarily referring to the same embodiment, although this may refer to the same embodiment.

As used herein, unless expressly specified that the use of numerical expressions such as " first ", "second "," third ", etc. is intended to describe a common object, such expressions refer to similar objects of different instances And is not meant to imply that the object being described is in a predetermined order either temporally or spatially in order or in any other way.

Embodiments may include an orthogonal frequency division multiplexing (OFDM) system operating in a frequency band below 1 GHz. In many embodiments, physical layer logic may implement repetition logic that repeats a portion of the data stream to increase the capability of the receiving device to detect and decode the data stream. In some embodiments, the iterative logic may increase the range of establishing and maintaining a communication channel between the transmitting device and the receiving device. In many embodiments, the range can be extended in units of 1 km.

In some embodiments, to increase the capability of a receiving device to detect a communication signal from a transmitting device, the iterative logic may include a preamble repeater that increases the integration time for a short training field by a correlator of the receiving device, . ≪ / RTI > In another embodiment, the iterative logic may include a preamble repeater to repeat the short training field multiple times, e.g., 2 to 5 times. In another embodiment, the iterative logic may include a preamble repeater to repeat the long training field multiple times, e.g., 2 to 5 times. In some embodiments, the iterative logic may include a preamble repeater to repeat the signal field multiple times, e.g., 2 to 5 times. In yet another embodiment, the iterative logic may include a preamble repeater for repeating additional long training fields in the preamble several times, for example two to five times, Lt; RTI ID = 0.0 > payload. ≪ / RTI >

In some embodiments, the iterative logic may include a payload repeater. The payload repeater may repeat the payload several times, e.g., 2 to 5 times. In many embodiments, the payload repeater may repeat the data in the bit stream of the physical layer device before interleaving the data stream at the transmitter, and in the case of multiple stream embodiments, the transmitter may perform stream parsing ) Before repeating the data in the bit stream of the physical layer device. In another embodiment, the payload repeater may repeat OFDM symbols in the transmit chain before or after the OFDM symbol is transformed into the time domain. In another embodiment, a payload repeater may be used in the IEEE 802.11n / ac system in addition to the existing coding schemes in order to effectively repeat the payload in the transmission of the communication signal, for example, with a binary phase shift keying ). ≪ / RTI >

Another embodiment may include a receiving device having a correlator for correlating multiple short training fields (STF), long training fields (LTF), and SIG symbols to detect communication from the transmitting device. The receiving device may also include correction logic to correct the data stream from the communication signal based on multiple iterations of the data in the data stream. In some embodiments, the receiving device may perform initial parameter estimation with repetition of short training fields. In another embodiment, the receiving device may perform fine parameter estimation with repetition of a long training field.

In the frequency band below 1 GHz, the available bandwidth is limited, so an IEEE 802.11n / ac type system using bandwidths of 20, 40, 80 and 160 MHz may not be feasible in some regions. In many embodiments, the system has a bandwidth of about 1 to 10 MHz. In some embodiments, an IEEE 802.11n / ac type system may implement down-clocked to achieve lower bandwidth. In one example, many embodiments are down-clocked by N, e.g., 20 MHz, 40 MHz, 80 MHz, and 160 MHz divided by N, where N may have a value of, for example, 10 (i.e., 2, 4, 8, and 16 MHz bandwidth Operation). Embodiments may also implement 1 MHz bandwidth in other ways. In some embodiments, the tone count for the 2, 4, 8, and 16 MHz bandwidths will be based on the tone count of the IEEE 802.11ac system. In other embodiments, the tone count may be different from the tone count of the IEEE 802.11n / ac system, for example, by eliminating unnecessary tone counts at low bandwidths.

Some embodiments may provide, for example, indoor and / or outdoor “smart” grid and sensor services. For example, some embodiments may provide a sensor to meter the use of household electricity, water, gas and / or other facilities in a particular area and wirelessly transmit their service usage to a meter substation. Another embodiment utilizes home healthcare, clinic or hospital sensors for patients such as, for example, fall detection, pill bottle monitoring, weight monitoring, sleep apnea, blood glucose, heart rate, and the like. Vital signs and nursing related tasks may be monitored. Embodiments designed for such services generally require much slower data rates and much smaller (extremely small) power consumption than devices provided in IEEE 802.11n / ac systems.

Some embodiments reuse hardware devices and reduce implementation costs by reusing IEEE 802.11n / ac systems with novel features that meet the requirements of the slow data rates and extremely small power consumption described above. Other embodiments accumulate multiple streams. Some embodiments do not implement validated training fields and legacy signatures, and do not implement multiple user Multiple Input, Multiple Output (MIMO). And some embodiments employ beamforming.

The logic, modules, devices, and interfaces described herein will perform functions that may be implemented in hardware and / or code. Hardware and / or code may include software, firmware, microcode, processors, state machines, chipsets, or combinations thereof designed to perform such functions.

Embodiments enable wireless communication. Some embodiments to integrate the low-power wireless communication, e.g., Bluetooth ^®, wireless local area network (WLAN), wireless city area communications network (WMAN), wireless personal communication network (WPAN), a cellular network, the Institute of Electrical and Electronics Institute of Technical Engineers IEEE 802.11-2007, Information Technology—Telecommunications and Information Exchange Between Systems—LAN / MAN—Specific Requirements—Part 11: Wireless LAN Media Access Control (MAC) and Physical Layer (PHY) Specifications (http: // standards, ieee.org/getieee802/download/802.11-2007.pdf), and can integrate smart devices that enable communication across the network, messaging systems, and devices. Furthermore, some wireless embodiments may include a single antenna while other embodiments may employ multiple antennas.

Referring now to FIG. 1, a wireless communication system 1000 of one embodiment is shown. The wireless communication system 1000 includes a communication device 1010 that is wired or wirelessly connected to a network 1005. The communication device 1010 can communicate wirelessly with a plurality of communication devices 1030, 1050, and 1055 via the network 1005. [ Communications devices 1010, 1030, 1050, 1055 may include sensors, stations, access points, hubs, switches, routers, computers, laptops, notebooks, cellular phones, PDAs, or other wireless capable devices. Thus, the communication device is a mobile device or a stationary device. For example, the communication device 1010 may include a metered substation associated with water consumption in a village's home. Each of the village homes may include a communication device, such as, for example, communication device 1030, which may be integrated with or connected to the water usage meter. The communication device 1030 may initiate communications with the metering substation to transmit data related to the water usage and may reside substantially remote from the communication device 1010. [

The communication device 1030 repeats a short training field (STF) several times when initiating communication with the communication device 1010 to allow the communication device 1010 to detect the STF through a preamble repeater 1036, Expand the range you can. In some embodiments, the communication device 1010 may repeat a long training field (LTF) and a signal field (SIG) in the case of a single stream and an additional LTF in the case of a multiple stream communication . Repetition of the LTF can improve parameter estimates associated with long-range communications, such as frequency errors, timing errors, and channel estimation.

In many embodiments, the communication device 1030 may repeat payloads, such as data regarding usage of the water, via the payload repeater 1042 to facilitate data decoding by the communication device 1010. The preamble repeater 1036 and the payload repeater 1042 can generally be referred to as repeating logic in the physical layer.

The communication device 1010 may include a correlator that integrates the received signal to detect one STF from multiple STFs transmitted from the communication device 1030. [ The communication device 1010 may also include correction logic 1026 that utilizes multiple copies of the payload to determine an accurate representation of the payload.

In another embodiment, the communication device 1010 may enable data offloading. For example, a communication device that is a low-power sensor may communicate via, for example, Wi-Fi, another communication device, a cellular network, etc., for the purpose of reducing power consumption and increasing available bandwidth, Data offloading scheme. A communication device that receives data from a sensor, such as a weighing machine, may include a data offloading system that communicates over Wi-Fi, another communications device, a cellular network, etc., for the purpose of reducing congestion of the network 1005.

The network 1005 may represent an interconnection consisting of multiple networks. As an example, the network 1005 may be coupled to a WAN, such as the Internet or an intranet, or may connect wired or wirelessly interconnected local devices via one or more hubs, routers, or switches. In this embodiment, the network 1005 is communicatively connected with the communication devices 1010, 1030, 1050, 1055.

Communication devices 1010 and 1030 include memories 1011 and 1031, media access control (MAC) sublayer logic 1018 and 1038, and physical layer logic 1019 and 1039, respectively . Memories 1011 and 1031, such as a DRAM, may store a frame, a preamble, and a preamble structure, or portions thereof. A frame and preamble structure, referred to as a MAC layer protocol data unit (MPDU), can establish and maintain synchronized communications between a transmitting device and a receiving device.

The MAC sublayer logic 1018,1038 will generate a frame and the physical layer logic 1019 will generate a physical layer data unit (PPDU) based on the frame. More specifically, frame builders 1012 and 1032 will generate frames and data unit builders 1013 and 1033 in physical layer logic 1019 will generate PPDUs. The data unit builders 1013 and 1033 are configured to provide a frame generated by the frame builders 1012 and 1032 to prefix the payload to be transmitted over one or more RF channels via the antenna arrays 1024 and 1044. [ Lt; RTI ID = 0.0 > PPDU < / RTI >

Data unit builders 1013 and 1033 may include preamble repeaters 1016 and 1036, respectively. The preamble repeaters 1016 and 1036 allow to extend the communication range between devices such as the communication devices 1010 and 1030, for example. Preamble repeaters 1016 and 1036 may generate preambles in the STF (in some embodiments, LTF) and signal fields of multiple concatenation sequences. For example, the preamble repeaters 1016 and 1036 may generate PPDUs that include a preamble having STFs of five concatenation sequences. In some embodiments, the preamble repeaters 1016,1036 may generate a preamble that includes five STFs, five LTFs, and five signal fields with respect to the PPDU. In another embodiment, a different number of STF, LTF, and signal fields may be included in the preamble of the PPDU.

The communication devices 1010, 1030, 1050, 1055 will each include a transceiver (RX / TX) such as, for example, transceivers 1020, 1040. In many embodiments, transceivers 1020 and 1040 implement orthogonal frequency division multiplexing (OFDM). OFDM is a method of encoding digital data on multiple carrier frequencies. OFDM is a frequency division multiplexing scheme used for digital multi-carrier modulation. A very large amount of orthogonal subcarrier signals in close proximity are used to carry data as OFDM symbols. An OFDM symbol is divided into several parallel data streams or channels, one for each subcarrier. Each subcarrier is modulated according to a modulation scheme at a low symbol rate to maintain the same total data rate as a conventional single carrier modulation scheme within the same bandwidth.

An OFDM system uses some carriers or "tones" for functions including data, pilot, guard, and nulling. The data tone is used to convert information between the transmitter and receiver over one of the channels. Pilot tones are used to maintain the channel and provide information about time / frequency and channel tracking. Guard tones are inserted between symbols such as STF and LTF to prevent intersymbol interference (ISI) during transmission, since such intersymbol interference is likely to result in multipath distortion. This guard tone also helps the signal conform to the spectral mask. Nulling of direct component (DC) can be used to simplify direct conversion receiver design.

Each transceiver 1020, 1040 includes an RF transmitter and an RF receiver. In this embodiment, each RF transmitter includes payload repeaters 1022 and 1042, and each RF receiver includes correction logic 1026 and 1046. [ Payload repeaters 1022 and 1042 include logic that includes repetition of payloads in the transmission of PPDUs. In some embodiments, the payload repeaters 1022 and 1042 are configured to repeat the data repeatedly before the bitstream enters the interleaver and, if the bitstream is a multiple bitstream, before the bitstream enters the stream parser. May include vector repetition logic to concatenate the bitstream into a bitstream.

In another embodiment, the payload repeaters 1022 and 1042 may include symbol repetition logic that generates one or more symbol repetitions in the transmit chain, which generates a symbol in the transmit chain as a time domain If it is before the conversion, it will perform in the frequency domain. If it is after the conversion, it will perform in the time domain. In another embodiment, payload repeaters 1022 and 1042 will include a new modulation and coding scheme. This new modulation and coding scheme may include binary phase shift keying (BPSK) at a coding rate of 1/4 which effectively repeats the payload in the code domain.

Correction logic 1026 and 1046 will provide logic to the receiver to take advantage of the repetition of the payload in the communication signal. In particular, the correction logic 1026, 1046 compares the different versions of the received payload to determine the correct version of the transmitted payload. In another embodiment, the correction logic 1026, 1046 enables demodulation of the communication signal transmitted from the transmitter over BPSK at a coding rate of 1/4.

1 illustrates a number of different embodiments, including a MIMO system having four spatial streams, wherein one or more communication devices 1010, 1030, 1050, 1055, including a SISO system, a SIMO system, and a MISO system, And degenerate systems including a receiver and / or a transmitter with an antenna. The wireless communication system 1000 of FIG. 1 is intended to represent an IEEE 802.11ah system. Likewise, devices 1010, 1030, 1050, 1055 are intended to represent IEEE 802.11ah devices.

In this embodiment, the antenna array 1024 refers to an array of discrete and independent exciting antenna elements. The signal to be applied to the elements of the antenna array 1024 causes the antenna array 1024 to radiate into one of four spatial channels. Each spatial channel thus formed will carry information to one or more communication devices 1030, 1050, 1055. Similarly, communication device 1030 includes a transceiver 1040 to transmit and receive signals to and from communication device 1010. The transceiver 1040 may include an antenna array 1044 and may communicate with an IEEE 802.11ah device.

1A illustrates one embodiment of a physical layer protocol data unit (PPDU) 1060 having a preamble structure 1062 for establishing communications between wireless communication devices, such as the communication devices 1010, 1030, 1050, 1055 of FIG. 1. Shows. PPDU 1060 includes a preamble structure 1062 that includes orthogonal frequency division multiplexing (OFDM) training symbols for a single MIMO stream, the next signal field, and additional OFDM training symbols for subsequent additional MIMO streams. This preamble structure 1060 may be followed by a data payload. In particular, the PPDU 1060 includes an STF 1064 followed by an X-th iteration of the STF 1065, an LTF 1066 followed by an X-th iteration of the LTF 1067, an X-iteration of the SIG field 1069, (SIG) 1068, and in some embodiments may also include additional fields 1070, such as additional LTF, to support multiple streams. The preamble structure 1062 is followed by data 1072, which is the payload of the PPDU 1060.

 The STF 1064 may include a number of short training symbols, such as 10 short training symbols with a length of 0.8 ms times N, where N is a down-clock from 20 MHz channel spacing. -clocking factor). As an example, this timing is twice the 10 MHz channel spacing. The total time frame for the STF 1064 at 20 MHz channel spacing is 8 ms times N. The STF * X 1065 repeats the STF 1064 one to four times, so the total time frame is 8 占 times N times X. In some embodiments, the preamble structure 1062 includes only a repetition of the STF 1064 and may not include repetition of the LTF 1066 and the SIG field 1068. In another embodiment, preamble structure 1062 includes repetition of LTF 1066 and / or SIG field 1068. [ This is illustrated in FIG.

The LTF 1066 will include one guard interval (GI) symbol and two long training symbols. The guard interval symbol will have a duration of 1.6 ms multiplied by N, and each of the long training symbols will have a duration of 3.2 ms multiplied by N at 20 MHz channel spacing. The total time frame for the LTF 1066 at 20 MHz channel spacing is 8 ms times N. The LTF * X 1067 repeats the LTF 1066 one to four times, so the total time frame is 8 占 times N times X.

The SIG field 1068 may include a guard interval (GI) symbol of 0.8 占 N and a signal field symbol of 7.2 占 N. Additional field 1070 may include, for example, one or more LTF symbols for additional MIMO if 4 占 N is required at 20 MHz channel spacing. In some embodiments, the additional field 1070 may be repeated one or more times in the preamble structure 1062. For example, the additional field 1070 may include additional LTF symbols for multi-stream antenna training, and such additional LTF symbols may be repeated X times for a duration of 4 占 하기 N times X times X per LTF symbol .

Data 1072 may include one or more MAC sublayer protocol data units (MPDUs), and may include one or more GIs. For example, data 1072 may include one or more symbol sets, where the symbol set is one GI symbol of 0.8 占 N at 20 MHz channel spacing, followed by 3.2 占 N at 20 MHz channel spacing Payload data.

Note that although the logic for the physical layer and MAC sublayer is illustrated as an independent unit interconnected with the transceiver, in some embodiments this logic may be integrated with one or more other devices to implement the same functionality.

2 illustrates one embodiment of an apparatus for transmitting orthogonal frequency division multiplexing (OFDM) based communication in a wireless network. The apparatus includes a MAC sublayer logic 201 and a transceiver 200 coupled to the physical layer logic 202. The MAC sublayer logic 201 generates a frame and the physical layer logic 202 encapsulates the frame in a preamble to generate a physical layer protocol data unit (PPDU) to transmit via the transceiver 200. For example, a frame builder generates a frame, where the frame includes a type field describing whether the frame is a management, control or data frame, a subtype field describing the function of the frame, . The control frame may include a ready-to-end frame or a clear-to-end frame. The management frame may include a beacon, a probe response, an association response, and a reassociation response frame type. And the data type field is designed to transmit data.

The preamble repeater 203 of the physical layer logic 202 will repeat the symbols of the STF, LTF and / or SIG fields in the preamble of the PPDU one or more times to extend the range in which the preamble is detected and decoded by the receiving device. For example, range extensions may be provided by increasing the number of sequences used in the STF. The new STF will be generated by concatenating multiple sets of time domain waveforms. The STF time-domain sequence is given in the time domain as:

From here,

N _Tx is the number of transmit antennas.

는 STF 페이로드의 톤의 개수이다.

Is the number of tones in the STF payload.

w (t) is a windowing function.

는 로테이션 함수(rotation function)이다.

Is a rotation function.

N _SR is the highest data subcarrier.

K is a subcarrier index.

는 부반송파 주파수 이격간격(subcarrier frequency spacing)이다.

Is the subcarrier frequency spacing.

In some embodiments, up to three time-domain sequences of the STF may be concatenated. Therefore, the extended STF will be generated by concatenating multiple symbols (the time domain sequence defined above). The three symbols will provide a total of 160 sample sequences of 2 MHz repeating a total of 12 times. Up to 5 symbols will provide 160 symbol sequences that repeat 20 times. If the time domain sequence is repeated three times, the final STF is given by:

The transceiver 200 includes a receiver 204 and a transmitter 206. The transmitter 206 includes one or more encoders 208, an interleaver 209, a modulator 210, an OFDM module 212 and a payload repeater 207. Note that some embodiments include a preamble repeater 203 and do not include a payload repeater 207.

The encoder 208 of the transmitter 206 receives data to be transmitted from the physical layer logic 202. The physical layer logic 202 may represent data to the transceiver 200 in blocks or symbols, e.g., as data bytes. Encoder 208 encodes the data using any of many known algorithms or algorithms to be developed in the future. Encoding is done to achieve one or more of many different purposes. For example, coding may be performed to reduce the average number of bits that must be transmitted to convert each symbol of information to be transmitted. Coding may be performed to reduce the likelihood of error in symbol detection at the receiver. Thus, the encoder may introduce redundancy for the data stream. Adding redundancy increases the channel bandwidth needed to transmit information but reduces errors and allows the signal to be transmitted at smaller power. The encoding may also include encryption for security.

In this embodiment, the encoder 208 may implement binary convolutional coding (BCC) or low density parity check coding (LDPC), or may implement other encodings. The output of the encoder 210 is supplied to the interleave 209 via one or more data streams. In some embodiments, a stream parser resides between the encoder 208 and the interleave 209, and may parse the data into multiple data streams.

In many embodiments, a payload repeater 207 may reside or be implemented between the encoder 208 and the interleave 209 to generate a repetition of the data stream so that the payload of the PPDU from the physical layer logic 202 is effectively contiguous . In some embodiments, the payload repeater 207 will include a repetition code. In the present embodiment, the data of the bit stream just before the interleaver 209 is repeated. In other embodiments, the sequence bits of the repeated data may be in reverse order. This approach improves performance by locating the same encoded bits at different times and different frequency bins of the transmit packet. Thus providing both frequency and time diversity.

The interleaver 209 interleaves the bits of the data stream (commonly referred to as a spatial stream in this step) to prevent a long sequence of adjacent noise bits from entering the decoder of the receiver. The interleaver 209 interleaves bits of data into the data stream by storing the data in rows of memory, such as a buffer, cache, or other memory. Thereafter, the interleaver 209 outputs the data coulumns. This column will contain bits of data from each row of data stored in memory. The number of rows and columns depends on the number of coded bits per subcarrier and the number of subcarriers for each spatial stream.

The modulator 210 of the transmitter 206 receives data from the interleaver 209. The purpose of the modulator 210 is to convert each block of binary data received from the encoder 208 into its own continuous waveform that can be transmitted by the antenna immediately upon up-conversion and amplification. The modulator 210 represents the received data block as a sinusoid of the selected frequency. More specifically, the modulator 210 maps data blocks to a corresponding discrete set of amplitudes in a sinusoid, or to a discrete set of phases in a sinusoid, or a discrete amount of frequency shift proportional to the frequency of the sinusoid. Map to a set. The output of the modulator 210 is a band pass signal.

In one embodiment, modulator 210 implements Quadrature Amplitude Modulation (QAM) representing two independent k-bit symbols from an information sequence as two orthogonal carriers, namely cos (2πft) and sin (2πft). QAM carries two digital bit streams by varying (modulating) the amplitude of two carriers using an amplitude-shift keying (ASK) digital modulation scheme. The two carriers are out of phase with each other by 90 °, so this is called an orthogonal carrier or an orthogonal component. The modulated waves are summed and the final waveform is a combination of PSK and ASK. A finite number of at least two phases and at least two amplitudes will be used.

In some embodiments, the modulator 210 maps blocks of data received from the encoder 208, mapping them using four points on a constellation spaced equidistantly around the circle, Modulation (Quadrature Phase-Shift Keying: QPSK) (256-QAM). With four phases, QPSK can encode two bits per symbol.

In an alternative embodiment, the modulator 210 may select two blocks or streams of data blocks received from the encoder 208 that are referred to as I-channels (for "in-phase") and Q- , Which is called Staggered Quadrature Phase Shift Keying (SQPSK). SQPSK is a method of phase shift modulation in which the signal carrier phase shift is 90 ° or 1/4 cycles at a time. The phase shift of 90 ° is known as the quadrature phase. The single-phase transition does not exceed 90 [deg.]. There are four states in SQPSK: 0 °, + 90 °, -90 ° and 180 °.

In another embodiment, the modulator 210 maps a block of data received at the encoder 280 into a discrete carrier phase set to generate a phase shift keying (PSK) signal. The N-phase PSK signal is generated by mapping a block of k = log ₂ N binary numbers of the input sequence to one of N corresponding phases θ = 2π (n-1) / n for n, a positive integer less than or equal to N. The final equivalent low-pass signal will be expressed by the following equation (1).

G (t-nT) is the fundamental pulse, and the shape of this pulse can be optimized to increase the likelihood of accurate detection at the receiver, for example by reducing intersymbol interference. This embodiment may use BPSK, which is the simplest form of PSK. BPSK uses two phases spaced 180 ° apart and is the most robust modulation of all PSKs because the demodulator eliminates the highest levels of noise or distortion that lead to inaccurate decisions. In BPSK, there are two signal phases, 0 ° and 180 °. Data is often differentially encoded prior to modulation.

In Figure 2, the modulator 210 is coupled to the payload repeater 207 to show that it includes an additional modulation and coding scheme in some embodiments, and the data in the data stream is effectively repeated one or more times for range extension . In this embodiment, the payload repeater 207 indicates that it implements BPSK at a coding rate of 1/4. Such modulation and coding schemes provide advantages of strong codes, thereby improving coding gain with frequency and diversity. In one embodiment, the code is generated (135, 135, 147, and 163) with a subsequent (octal) generator. According to the comparison, the free distance of the current 1/2 coding rate is 10, and the free distance is 20 in the case of the new 1/4 coding rate. Thus, using this new code doubles the free distance.

The output of the modulator 209 is supplied to the OFDM module 212. OFDM module 212 includes a space time block coding (STBC) module 211, a digital beamforming (DBF) module 214 and an inverse fast Fourier transform (IFFT) module 215 . STBC module 211 receives constellation points corresponding to one or more spatial streams from modulator 209 and spreads the spatial streams to more space-time streams (commonly referred to as data streams). In some embodiments, the STBC 211 may be controlled to process the entire spatial stream, for example, if the number of spatial streams is the maximum number of space-time streams. Other embodiments may omit STBC.

The OFDM module 212 represents or maps the modulated data formed of OFDM symbols as a plurality of orthogonal subcarriers. In some embodiments, the OFDM 212 includes a digital beamforming (DBF) module 214. Digital beamforming technology is employed to neutralize the efficiency and capacity of wireless systems. Generally, digital beamforming uses digital signal processing algorithms that transmit system performance to an array of antenna elements and operate on received signals. For example, a plurality of spatial channels may be formed, each spatial channel being independently steered to maximize the signal power transmitted and received at each of the plurality of user terminals. Digital beamforming will also be applied to minimize multi-path fading and not to accept co-channel interference.

OFDM module 212 may include an inverse Fourier transform module that performs an inverse discrete Fourier transform (IDFT) on the OFDM symbol. Between the STBC 211 and the IFFT 215, the payload repeater 207 generates 3 to 5 OFDM symbol repetitions in the frequency domain in the data stream, and each OFDM symbol is transmitted to the transmitter block following the modulator 210 Such repetition code repeated at the end improves the detection and decoding of the payload. In some embodiments, this repetition is implemented solely for the MCS0 configuration, that is, for BPSK with a 1/2 coding rate. This method can improve the signal-to-noise ratio (SNR) of the combined symbols, for example improving the SNR by 3 dB for a single symbol. Since the symbols are repeated at or near the end of the transmit chain, the same bits will be aligned to the same frequency bin, and the symbols will be temporally adjacent to each other. In other embodiments, more or less such symbols may be generated.

In the present embodiment, the IDFT may include an IFFT module 215 to perform an IFFT on the data. For example, in a 1 MHz bandwidth operation, the IFFT module 215 will perform a 32-point inverse FFT on the data stream.

Between the IFFT 215 and the guard interval insertion, for example, the payload repeater 207 may use 3 to 5 OFDM symbol repetitions in the time domain instead of generating repetitions in the frequency domain to improve the detection and decoding of the payload, Lt; / RTI > This process will similarly repeat each OFDM symbol at or near the end of a transmission block following modulator 210. [ In some embodiments, this repetition is implemented only for BPSK modulation with a 1/2 coding rate.

The output of the IFFT module 215 may be upconverted to a higher carrier frequency or integrated with the upconversion. Shifting the signal to a fairly high frequency prior to transmission allows the use of an antenna array of practical size. In other words, the higher the transmission frequency, the smaller the antenna can be. Thus, the upconverter multiplies the modulated waveform by a sinusoidal curve to obtain a signal having a carrier frequency that is the sum of the center frequency of the waveform and the frequency of the sinusoidal curve. This operation is based on trigonometric functions.

The signal of sum frequency A + B is passed, and the signal of difference frequency A-B is filtered out. Therefore, a band pass filter is provided so that only information centered on the carrier (sum) frequency is transmitted and the remaining information is ideally filtered.

The transceiver 200 may also include a diplexer 216 connected to the antenna array 218. Therefore, in this embodiment, a single antenna array is used for both transmission and reception. At the time of transmission, the signal passes through the diplexer 216, and the antenna is driven by the up-converted information-containing signal. During transmission, the diplexer 216 prevents the signal to be transmitted from entering the receiver 204. Upon reception, the information bearing signal received at the antenna array carries the signal from the antenna array to the receiver 204 past the diplexer 216. At this time, the diplexer 216 blocks the received signal from entering the transmitter 206. Thus, the diplexer 216 acts like a switch that selectively connects the antenna array elements to the receiver 204 and the transmitter 206.

Antenna array 218 emits information-bearing signals into time-varying, spatially distributed electromagnetic energy that is received by the antenna array of the receiver. In this case, the receiver may extract information from the received signal. An array of antenna elements can generate multiple spatial channels that can be adjusted to optimize system performance. Advantageously, the multiple spatial channels of the radiation pattern at the receive antenna may be separated into different spatial channels. Therefore, the radiation pattern of the antenna array 218 can be very selective. Antenna array 218 may be implemented using printed circuit board wiring techniques. For example, microstrips, striplines, slotlines and patches are all available for the antenna array 218.

The transceiver 200 may include a receiver 204 for receiving, demodulating and decoding information-bearing signals. Receiver 204 includes a correlator 223 that can take advantage of the repetition symbols of the preamble, e.g., as repetitions of STF, LTF, and / or SIG symbols. The correlator 223 will take advantage of the repetition symbol by integrating the incoming signal over a longer or extended time period associated with the repetition symbol to detect the preamble of the communication signal from the transmitter, The correlator 223 will compare the repetition of the STF, LTF and / or signal field symbols with the known sequences of these STF, LTF and signal fields to identify the preamble of the communication signal and consequently to detect the communication signal.

For example, a data collection station compliant with IEEE 802.11ah for farms will periodically receive data from a low power sensor with an integrated wireless communication device compliant with IEEE 802.11ah. The sensor enters the low power mode for a period of time, is activated to periodically collect data, and will periodically communicate with the data collection station to transmit the data collected by the sensor. In many embodiments, the sensor determines a preamble in which the STF sequence is repeated three to five times. In some embodiments, the sensor generates a PPDU in which the payload is repeated to improve detection and decoding of data collected by the sensor. The correlator 223 of the data collection station will then compare the 3 to 5 repetitions of the preamble with a known sequence of STF, LTF and / or signal fields to detect the content sent from the sensor and received.

The receiver 204 may include one or more of an OFDM module 222, a demodulator 224, a deinterleaver 225, a decoder 226 and a correction logic 230. The OFDM module 222 extracts signal information as OFDM symbols from a plurality of subcarriers on which information-containing signals are modulated.

The OFDM module 222 may include a Fast Fourier Transform (FFT) module 219, a DBF module 220, and an STBC module 221. The received signal is supplied from the antenna element 218 to the FFT module 219, so that the communication signal is converted into the frequency domain in the time domain. In some embodiments, the correction logic 230 receives multiple iterations of the payload symbol and solves the error of this symbol based on the repetition of the symbol received by the receiver 204 before or after the FFT module 219 To determine an error corrected symbol. The DBF module 220 converts N antenna signals into L information signals. The STBC module 221 will then convert the data stream of the space-time stream into a spatial stream. In one embodiment, demodulation is performed in parallel on the output data of the FFT. In another embodiment, an independent demodulator 224 performs demodulation independently.

Demodulator 224 demodulates the spatial stream. Demodulation is the process of extracting data from a spatial stream and generating a demodulated spatial stream. The demodulation method depends on the manner in which the information is modulated in the received carrier signal, and this information is contained in the TXVECTOR contained in the communication signal. Thus, for example, if the modulation was BPSK, demodulation would convert the phase information into a binary sequence with phase detection. In this embodiment, demodulator 224, in conjunction with correction logic 230, allows demodulator 224 to generate a new modulation and coding scheme, i.e., a coding rate of 1/4, in addition to the existing coding scheme in the IEEE 802.11n / ac system Lt; RTI ID = 0.0 > BPSK. ≪ / RTI >

The demodulator 224 provides a sequence of information bits to the deinterleaver 225. The deinterleaver 225 will store the bits of data in the column and remove the data in the row to deinterleave the data. In some embodiments, the correction logic 230 will perform error correction on the iteration of the data in the data stream after being output by the deinterleaver 225.

The decoder 226 decodes the data received from the demodulator 224 and sends the decoded information MPDU to the physical layer logic 202. In some embodiments, the correction logic 230 will perform error correction on the data stream.

Those skilled in the art will appreciate that the transceiver may include various additional functions not shown in FIG. 2, and the receiver 204 and the transmitter 206 are not configured as a single transceiver and are separate devices. It will be appreciated. For example, embodiments of a transceiver may include a DRAM, a reference oscillator, a filtering circuit, spatial mappers, a cyclic shift insertion module, a guard interval insertion module, a synchronization circuit, Multiple amplification steps, and the like. In addition, some of the functions shown in FIG. 2 may be integrated. For example, digital beamforming may be integrated with orthogonal frequency division multiplexing.

In many embodiments, the payload repeater 207 may be implemented in one location in the data stream, for example, in front of the interleaver 209, in the modulator 210, or in front of the IFFT 215 in the OFDM 212 Can be implemented later. In another embodiment, the payload repeater 207 may be implemented in more than one location along the data stream. Correction logic 230 may also be implemented in one embodiment in some embodiments such as before FFT 219, after FFT 219, inside demodulator 224 or deinterleaver 225, . ≪ / RTI > In another embodiment, the correction logic 230 may be implemented in one or more locations.

FIG. 3 illustrates one embodiment of a flowchart 300 for transmitting communications to the transmitter illustrated in FIG. Flowchart 300 illustrates four alternate flows. In particular, steps 317, 327, 332, 337 represent four selectable replacement processes. In other embodiments, one or more of these alternative processes may be included in the same process.

Flowchart 300 begins by receiving a frame from a frame builder (step 305). The MAC sublayer logic generates a frame to be transmitted to the other communication device, and when this frame is transferred as MPDU to the data unit builder of the physical layer logic, the physical layer logic converts this data into a packet that can be transmitted to another communication device . The data unit builder generates a preamble, which includes three to five concatenated iterations of the STF, LTF and / or SIG field sequences (step 307). The data unit builder then uses this preamble to encapsulate the PSDU (MPDU from the frame builder) to form the PPDU for transmission (step 310). In some embodiments, one or more MPDUs may be encapsulated in a PPDU.

The flowchart 300 proceeds to the step where the transmitter, e.g., transmitter 206, receives the PPDUs from the physical layer logic. The transmitter may encode the PPDU in binary convolutional coding (BCC) or low-density parity check coding (LDPC) to control errors in transmission of data (step 315). More specifically, the transmitter may encode the PPDU over one or more of the encoding schemes described in the preamble of the PPDU, such as, for example, BCC or LDPC.

After encoding of the frame, in some embodiments, the transmitter may repeat the bitstream more than once to provide payload repetition (step 317). In some embodiments, the transmitter may generate a repeated sequence of bits in the bitstream in reverse order.

The transmitter will interleave the frame into one or more data streams (step 320). For example, the interleaver of the transmitter may receive this frame with data of multiple data streams, for example from a frame parser. The interleaver then interleaves the data bits for transmission by storing the data from the data stream in a row of memory and outputting the data as a data stream from a column of memory.

The transmitter modulates the data stream through the modulation and coding scheme specified in the preamble, such as BPSK, 16-QAM, 64-QAM, 256-QAM, QPSK or SQPSK (step 325). For example, a constellation mapper will map a sequence of bits of the data stream to constellation points (complex numbers). In some embodiments, the transmitter modulates the data stream with BPSK modulation at a coding rate of 1/4 (step 327), effectively repeating the symbols of the payload.

The OFDM module of the transmitter will map the constellation point of the data stream as an OFDM symbol to the transmit chain (step 330). For example, the OFDM module may include an STBC encoder that maps constellation points of a spatial stream to a space-time stream, and a spatial mapper that maps the space-time stream to a transmission chain, which is a subcarrier and an encoded OFDM symbol. The spatial mapper provides direct mapping, where the constellation points from each spatiotemporal stream are mapped directly to the transmit chain (one-to-one mapping). Spatial mapping provides a spatial extension in which the vector of constellation points from all spatial-temporal streams is extended through a matrix multiplication to generate an input of the OFDM symbol for all transmission chains. Alternatively, the spatial mapper may provide a DBF, where each vector of constellation points from all spatial-temporal streams is multiplied by a vector steering matrix to generate an OFDM symbol as input to the transmit chain.

In some embodiments, after mapping the data stream as an OFDM symbol, the symbols may be repeated (step 332) to include a repetition of the payload of the transmit chain (step 332) to allow the receiver to effectively detect and decode the payload Extend the range.

The transmitter will transform the OFDM symbol into the time domain through an inverse Fourier transform (step 335). In some embodiments, after converting the symbol to the time domain, the symbols will be repeated to include the repetition of the payload of the transmit chain (step 337). Thereafter, the transmitter upconverts the OFDM symbol for transmission (step 340), transmits the OFDM symbol to the antenna (s) as a communication signal, and the antenna (s) (Step 345). If there are more frames to transmit (step 360), the process will start again at step 305.

FIG. 4 illustrates one embodiment of a flowchart 400 for detecting and receiving communications with the receiver illustrated in FIG. The flowchart 400 illustrates four alternate flows. In particular, steps 412, 417, 427, 433 represent four selectable replacement processes. In other embodiments, one or more of these alternative steps may be included in the same process.

Flow diagram 400 begins with the receiver detecting a communication signal by correlating the communication signal with a known sequence of preambles, e.g., receiver 204 (step 403). The flow diagram 400 proceeds to receiving a communication signal from a transmitter via one or more antenna (s), such as, for example, an antenna element of the antenna array 218 (step 405). The receiver downconverts the communication signal to a low frequency (step 410). Thereafter, in some embodiments, the receiver may perform error correction on the symbols of the payload (step 412), taking advantage of the repetition of the payload to determine the error corrected symbols.

The receiver will convert the communication signal to the frequency domain via FFT (step 415). In some embodiments, the receiver may perform error correction on the symbols of the payload after converting the symbols to the frequency domain based on repetition of the payload symbols (step 417).

The transmitter extracts an OFDM symbol from the communication signal (step 420) and demodulates the OFDM symbol to generate a data stream of demodulated symbols (step 425). For example, a demodulator such as demodulator 224 demodulates the data stream via, for example, BPSK, 16-QAM, 64-QAM, 256-QAM, QPSK or SQPSK. In some embodiments, the demodulator will demodulate the data stream based on BPSK modulation at a coding rate of 1/4 (step 427).

The deinterleaver receives the demodulated data stream and deinterleaves the data stream by, for example, storing the data of the column and removing the data of the row. In some embodiments, the receiver deinterleaves the data stream and then performs error correction on the data stream to correct errors in the repeated symbols in the data stream (step 433).

For example, a decoder, such as decoder 226, decodes the data stream from the demodulator to determine the PPDU, e.g., via BCC or LDPC (step 435). The transmitter then extracts the MPDU from the PPDU (step 440), and sends the MPDU to the MAC sublayer logic, e.g., the MAC sublayer logic 201 (step 445).

Another embodiment is implemented as a program product implementing the systems and methods described with reference to FIGS. Some embodiments may take the form of hardware in its entirety, or may take the form of software in its entirety, or may take the form of both hardware and software elements. One embodiment is implemented in software, where the software is not limited to firmware, resident software, microcode, or the like.

Further, embodiments may take the form of a program product (or machine accessible product) accessible from a computer usable or computer readable medium for use by or in connection with a computer or any instruction execution system. . To this end, a computer usable or computer readable medium may be any device that can contain, store, communicate, propagate or transport a program for use by or in conjunction with an instruction execution system, apparatus or device.

The medium may be an electronic system, magnetic system, optical system, electromagnetic system, infrared system or semiconductor system (or apparatus or device). Examples of computer readable media include semiconductor or solid state memory, magnetic tape, removable computer diskettes, RAM, ROM, magnetic hard disks, and optical disks. Examples of current optical discs are CD-ROM, CD-R / W and DVD.

A data processing system suitable for storing and / or executing program code will include at least one processor coupled directly or indirectly to a memory element via a system bus. Memory elements include local memory, mass storage, and cache memory that are used during the actual execution of program code, which caches at least some program code temporarily to reduce the number of times the code must be retrieved from mass storage during execution. Save as.

The aforementioned logic is part of the design for the integrated circuit chip. Chip designs are written in a graphical computer programming language and stored on computer storage media (eg, virtual hard disks such as disks, tapes, physical hard disks, or storage access networks). If the designer does not manufacture the chip or the photolithographic mask used to manufacture the chip, the designer sends the final design by physical means (eg by providing a copy of the storage medium that stores the design). Or directly or indirectly to such an entity electronically (eg via the Internet). The stored design is then converted into an appropriate format (eg GDSII) for production.

The final IC chip may be distributed by the manufacturer in the form of a raw wafer such as a bare die (i. E., A single wafer with multiple unpackaged chips) or in the form of a package. When deployed in a packaged form, the chip may be mounted in a single chip package (e.g., plastic carrier or advanced carrier with leads attached to the motherboard) or in a multichip package (e.g., surface interconnects and embedded interconnects). Ceramic carriers having one or both of them). In some cases, the chip is then integrated with other chips, separate circuit elements and / or other signal processing devices as (a) an intermediate product, such as a motherboard, or (b) as a final product.

Claims (30)

Generating, by physical layer logic, a preamble for orthogonal frequency division multiplexing communications, the preamble comprising repetitions of a short training field. Having a repetition of a long training field and a repetition of a signal field—and,
Receiving a frame generated by medium access control sublayer logic;
Encapsulating, by the physical layer logic, the frame into the preamble to generate a physical layer protocol data unit.
Way.
The method of claim 1,
Transmitting, by an antenna, the frame encapsulated with the preamble
Way.
The method of claim 1,
Storing, by the medium access control sublayer logic, the preamble in a memory.
Way.
The method of claim 1,
Generating the preamble includes generating a preamble having repetitions of additional training sequences for additional streams, wherein the additional training sequences follow the signal field within the preamble.
Way.
The method of claim 1,
Generating a repetition of the payload of the physical layer protocol data unit by repeating the data of the payload of the physical layer protocol data unit in a data stream, wherein repeating the data of the payload comprises the data stream. Prior to interleaving to reverse the bits of the repeated data.
Way.
The method of claim 1,
Generating a repetition of the payload of the physical layer protocol data unit by repeating data of the payload of the physical layer protocol data unit in a data stream, wherein repeating the data of the payload is a modulation of the data. After and before insertion of guard intervals
Way.
The method of claim 1,
Modulating the data stream with binary phase shift keying modulation at a coding rate of 1/4;
Way.
A memory,
A data unit builder coupled to the memory, generating a preamble, receiving a frame generated by media access control sublayer logic, and encapsulating the frame with the preamble to generate a physical layer protocol data unit. Preamble includes repetition of the short training field, repetition of the long training field, and repetition of the signal field.
Device.
The method of claim 8,
A transmitter coupled to the data unit builder to transmit the frame encapsulated with the preamble
Device.
The method of claim 8,
A data unit builder memory is coupled to the memory to store at least a portion of the preamble
Device.
The method of claim 8,
The data unit builder is further configured to generate a preamble having a repetition of an additional training sequence for an additional stream, wherein the additional training sequence is subsequent to the signal field within the preamble.
Device.
The method of claim 8,
Further comprising a transmitter for generating a repetition of the payload of the physical layer protocol data unit by repeating the data of the payload of the physical layer protocol data unit in a data stream, wherein repeating the data of the payload comprises the data stream. Prior to interleaving to reverse the bits of the repeated data.
Device.
The method of claim 8,
Further comprising a transmitter for generating repetition of the payload of the physical layer protocol data unit by repeating data of the payload of the physical layer protocol data unit in a data stream, wherein repeating the data of the payload is a modulation of the data. After and before insertion of the guard interval
Device. The method of claim 8,
Further comprising a transmitter for modulating the data stream with binary phase shift modulation at a code rate of 1/4
Device.
A data unit builder that generates a preamble, receives a frame generated by media access control sublayer logic, and encapsulates the frame with the preamble to generate a physical layer protocol data unit, wherein the preamble is a repetition of a short training field, a long training field. Has a repetition of and a repetition of the signal field
A transmitter coupled to the data unit builder,
An antenna array for transmitting the frame from the data unit builder;
system.
The method of claim 15,
The data unit builder is further configured to generate a preamble having a repetition of an additional training sequence for an additional stream, wherein the additional training sequence is subsequent to the signal field within the preamble.
system.
The method of claim 15,
The transmitter includes a payload repeater that generates a repetition of the payload of the physical layer protocol data unit by repeating data of the payload of the physical layer protocol data unit in a data stream, wherein Repeating data is performed prior to interleaving the data stream to reverse the bits of the repeated data.
system.
The method of claim 15,
The transmitter includes a payload repeater that generates repetition of the payload of the physical layer protocol data unit by repeating data of the payload of the physical layer protocol data unit in a data stream, wherein the payload repeater repeats the data of the payload. Is performed after the modulation of the data and before the insertion of the guard interval.
system.
The method of claim 15,
The transmitter includes a modulator for modulating the data stream with binary phase shift modulation at a code rate of 1/4.
system.
A machine-accessible product comprising a medium containing instructions for orthogonal frequency division multiplexed communication, the instructions causing a transmitter to perform an action in response to execution of the command, wherein the action is
Repeating the payload of the physical layer protocol data unit by repeating the data of the payload of the physical layer protocol data unit in a data stream.
Machine accessible product.
22. The method of claim 21,
The act of generating a repetition of the payload of the physical layer protocol data unit comprises repeating the data of the payload in the data stream before interleaving the data stream to reverse the bits of the repeated data. Including repeating the payload of the layer protocol data unit
Machine accessible product.
22. The method of claim 21,
The operation of generating a repetition of the payload of the physical layer protocol data unit may be performed by repeating data of the payload in the data stream after modulation of the data and before insertion of a guard interval. Contains actions that cause repetition of the load
Machine accessible product.
Receiving, by correlation logic, a communication signal comprising a preamble having a repetition of a short training field, a repetition of a long training field, and a repetition of a signal field;
Comparing, by the correlation logic, a repetition of the short training field of the preamble with a known short training field sequence to detect the communication signal.
Way.
24. The method of claim 23,
Receiving, by an antenna, a payload encapsulated with the preamble
Way.
24. The method of claim 23,
Performing error correction on the payload based on repetition of the payload of the communication signal;
Way.
24. The method of claim 23,
Performing initial parameter estimation by repeating the short training field;
Way.
24. The method of claim 23,
Performing fine parameter estimation with repetition of the long training field;
Way.
An antenna,
Coupled to the antenna to receive a communication signal comprising a preamble having a repetition of a short training field, a repetition of a long training field, and a repetition of a signal field, and repetition of the short training field of the preamble and a known short training field sequence. A receiver that compares and detects the communication signal
Device.
29. The method of claim 28,
The receiver includes logic to perform error correction on the payload based on the repetition of the payload of the communication signal.
Device.
29. The method of claim 28,
The receiver includes logic to perform initial parameter estimation with repetition of the short training field and fine parameter estimation with repetition of the long training field.
Device.

Images